Technical data

Organization Blocks
System Software for S7-300/400 System and Standard Functions - Volume 1/2
1-8 A5E00709327-01
Conditions That Affect Time-of-Day Interrupt OBs
Since a time-of-day interrupt occurs only at specified intervals, certain conditions
can affect the operation of the OB during the execution of your program. The
following table shows some of these conditions and describes the effect on the
execution of the time-of-day interrupt OB.
Condition Result
Your program calls SFC29 (CAN_TINT) and
cancels a time-of-day interrupt.
The operating system clears the start event
(DATE_AND_TIME) for the time-of-day interrupt. You
must set the start event again and activate it before the
OB can be called again.
Your program attempted to activate a time-of-
day interrupt OB, but the OB was not loaded
on the CPU.
The operating system calls OB85. If OB85 has not been
programmed (loaded on the CPU), the CPU changes to
the STOP mode.
When synchronizing or correcting the system
clock of the CPU, you set the time ahead and
skipped the start event date or time for the
time-of-day OB.
The operating system calls OB80 and encodes the
number of the time-of-day OB and the start event
information in OB80.
The operating system then runs the time-of-day OB
once, regardless of the number of times that this OB
should have been executed. The start event information
of OB80 shows the DATE_AND_TIME that the time-of-
day OB was first skipped.
When synchronizing or correcting the system
clock of the CPU, the time was set back so
that the start event, date, or time for the OB is
repeated.
S7-400-CPUs and CPU 318:
If the time-of-day OB had already been activated before
the clock was set back, it is not called again.
S7-300-CPUs: The time-of-day OB is executed.
The CPU runs through a warm or cold restart. Any time-of-day OB that was configured by an SFC is
changed back to the configuration that was specified in
STEP 7.
If you have configured a time-of-day interrupt for a one-
time start of the corresponding OB, set it with STEP 7,
and activated it, the OB is called once after a warm or
cold restart of the operating system, if the configured
start time is in the past (relative to the real-time clock of
the CPU).
A time-of-day OB is still being executed when
the start event for the next interval occurs.
The operating system calls OB80. If OB80 is not
programmed, the CPU changes to the STOP mode.
If OB80 is loaded, both OB80 and the time-of-day
interrupt OB are first executed and then second the
requested interrupt is executed.